This investigation concerns several aspects of the postsynaptic receptor site for gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter in the mammalian central nervous system (CNS). Evidence is presented to indicate that the integrity of this receptor site in certain areas of the rat CNS is influenced by adrenocorticoids. Using ligand binding techniques, the kinetics and specificity of this alteration are examined. In addition, the influence of corticoids on other biochemical parameters of the GABAergic system are studied in an attempt to determine the mechanism of this receptor phenomenon. This proposal also deals with the development of a simple, biochemical procedure which could be used to rapidly screen and differentiate GABA receptor agonists and antagonists by analyzing the interaction of drugs using receptor binding. In addition, experiments are described to study the interaction of some recently developed GABA antagonists and agonists to assess their specificity, the nature of their interaction and, using these compounds, to search for pharmacologically distinct GABA receptor sites in the CNS. The results of this study may aid in the development of therapeutically efficacious agents for the treatment of neurological disorders involving abnormal GABAergic activity.